1990 Mercury Grand Marquis Engine Miss and Runs Bad

Reader Question
Howdy Austin, I seem to have a real problem on my hands, and not a clue what is causing it. I have a 1990 Mercury, Grand Marquis that has an engine tick for the first 2 to 3 seconds after it is started up. The car has about 150,000 miles on it. But the real problem I have is, the car runs great for about 5 miles when it is cold. After that the car has a severe miss but only in drive or overdrive. When it misses it causes a severe jerk inside for passengers. When I start out in first then second gear it runs fine but shortly after going into drive it starts missing and jerking the car. If I mash the accelerator to the floor and go into passing gear it will quit missing. When back in drive or O/D if the load on the engine is kept light, (as in just maintaining speed) the missing will back off. This is not an old problem,it just started about 2 weeks ago.

Also the exhaust donut is leaking. It started leaking about 1 1/2 months ago and been getting worse. I was going to change it when I put it up on the rack for its oil change. Could this cause a lack of back pressure and make it miss like this? I had heard that lack of back pressure could cause this but sounds like a fairy tale to me. Please put me back on the right track. Thank you very much for any answer. Rick

Hello there Rick,

Thanks for your email. I would suspect your exhaust donut leak is your ticking noise after start up, have it replaced at your local exhaust shop and see if the problem goes away. If not, you might have a noisy lifter, located in the top of the cylinder head. Try adding a can of Marvel Mystery Oil to your engine oil and see if that helps.

The engine miss, I would FIRST take a hard look at the spark plugs AND spark plug wires. From your email I would HIGHLY suspect a faulty spark plug wire. If the wires have more than 50K miles on them….replace them as maintenance anyway, and it would be a good idea to inspect and replace the spark plugs as well.

Keep me posted.

Blessings,

Austin C. Davis